Method and design for high shot density perforating gun

ABSTRACT

A perforating gun includes a plurality of shaped charges located at a first distance from a detonator along a plurality of detonating cords and forming a first group, wherein the first group of shaped charges is configured to be detonated simultaneously. The plurality of detonating cords are of the same length.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 61/427,710, entitled, “Method and Design for High Shot Density Perforating Gun” and filed on Dec. 28, 2010, which is incorporated herein by reference.

BACKGROUND

1. Field of the Disclosure

Embodiments disclosed herein relate generally to downhole tools. In particular, embodiments disclosed herein relate to perforating guns.

2. Background Art

To complete a well for purposes of producing fluids (such as hydrocarbons) from a reservoir, or to inject fluids into the reservoir, one or more zones in the well are perforated to allow for fluid communication between the wellbore and the reservoir. Normally, perforation is accomplished by lowering a perforating gun string that has one or more perforating guns to the desired intervals within the well. Activation of the one or more guns in the perforating gun string creates openings in any surrounding casing and extends perforations into the surrounding formation.

High shot density perforating guns, which have a higher packing density of shaped charges (e.g., more than four shots per foot), may experience charge interference among the shaped charges, which may hinder performance of the shaped charges and affect the quality of the perforations. Charge interference among shaped charges may result from a small delay in detonation between successive shaped charges, which allows fragments of the previously detonated adjacent shaped charge to interfere with the formation of the perforation in a subsequent shaped charge.

Generally, perforating guns may be designed with sufficient spacing between adjacent shaped charges to reduce charge interference and allow greater penetration depth into the formation by the shaped charges. Despite many valuable contributions from the art, it would be beneficial to develop a perforating gun which allows for a higher packing density of shaped charges.

SUMMARY OF THE DISCLOSURE

In one aspect, embodiments disclosed herein relate to a perforating gun including a plurality of shaped charges located at a first distance from a detonator along a plurality of detonating cords and forming a first group, wherein the first group of shaped charges is configured to be detonated simultaneously.

In other aspects, embodiments disclosed herein relate to a method for manufacturing a perforating gun including positioning a plurality of shaped charges in a housing of the perforating gun, wherein the plurality of shaped charges are disposed at a first distance from a detonator, and connecting a plurality of detonating cords to each of the plurality of shaped charges, wherein the plurality of detonating cords are configured to provide simultaneous detonation of the plurality of shaped charges.

In other aspects, embodiments disclosed herein relate to a method for using a perforating gun including providing the perforating gun in a borehole, wherein the perforating gun comprises a plurality of shaped charges located at a first distance from a detonator along a plurality of detonating cords and forming a first group, wherein the first group of shaped charges is configured to be detonated simultaneously, and detonating the perforating gun to fire the plurality of shaped charges simultaneously.

Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of a perforating gun are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components.

FIG. 1 illustrates a tool string having a perforating gun in a conventional assembly.

FIG. 2 illustrates a schematic view of shaped charges in a conventional perforating gun.

FIG. 3 illustrates a schematic view of shaped charges in a perforating gun in accordance with one or more embodiments of the present disclosure.

FIG. 4 illustrates a schematic view of shaped charges in a perforating gun in accordance with one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

The following is directed to various exemplary embodiments of the disclosure. Although one or more of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, those having ordinary skill in the art will appreciate that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

Certain terms are used throughout the following description and claims refer to particular features or components. As those having ordinary skill in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first component is coupled to a second component, that connection may be through a direct connection, or through an indirect connection via other components, devices, and connections. Further, the terms “axial” and “axially” generally mean along or parallel to a central or longitudinal axis, while the terms “radial” and “radially” generally mean perpendicular to a central longitudinal axis.

Additionally, directional terms, such as “above,” “below,” “upper,” “lower,” etc., are used for convenience in referring to the accompanying drawings. In general, “above,” “upper,” “upward,” and similar terms refer to a direction toward the earth's surface from below the surface along a borehole, and “below,” “lower,” “downward,” and similar terms refer to a direction away from the surface along the borehole, i.e., into the borehole, but is meant for illustrative purposes only, and the terms are not meant to limit the disclosure.

Embodiments disclosed herein relate to perforating guns. In general, embodiments disclosed herein relate to a perforating gun in which a group of shaped charges having a particular spacing therebetween may be simultaneously detonated to avoid interference among the group of shaped charges. More specifically, embodiments disclosed herein may include multiple detonator cords that extend from one or more detonators, wherein the detonator cords are configured to allow simultaneous initiation of the group of shaped charges.

FIG. 1 illustrates a tool string 102 deployed in a wellbore 104. The tool string 102 includes a perforating gun 106 that has a carrier 108 having various shaped charges 110 (e.g., perforator charges or other explosive devices that form perforating jets) attached thereto. The perforating gun 106 is carried by a carrier line 116, which can be a wireline, slickline, coiled tubing, production tubing, and so forth. The carrier 108 may be an expendable carrier that is designed to shatter as a result of detonation of the shaped charges 110. An example of such an expendable carrier is a strip carrier, such as a carrier formed of a metal strip. In a different implementation, instead of mounting the shaped charges 110 on a strip carrier, the carrier can be a sealed housing that has an inner chamber in which the shaped charges are located, with the chamber being sealed against external wellbore fluids in the wellbore 104.

In the embodiment shown in FIG. 1, the shaped charges 110 may be provided in a sealed chamber of a carrier housing. Therefore, the shaped charges 110 are non-capsule shaped charges. In alternative embodiments, when the shaped charges 110 are mounted to the carrier strip 108 such that the shaped charges 110 would be exposed to wellbore fluids, the shaped charges 110 are capsule shaped charges that have a capsule to provide a fluid seal to protect the internal components of the shaped charges 110 against the wellbore fluids.

The shaped charges 110 in the example of FIG. 1 may be ballistically connected to a detonating cord 112. The detonating cord 112 is connected to a firing head 114. When activated, the firing head 114 initiates the detonating cord 112, which in turn causes detonation of the shaped charges 110.

In a different implementation, the detonating cord 112 may be replaced with one or more electrical wires connecting the firing head 114 to the shaped charges 110. Electrical signal(s) may be sent by the firing head 114 over the one or more electrical wires to activate the shaped charges 110. For example, the shaped charges 110 may be associated with electrically-activated initiators (e.g., electrical foil initiators or “EFI's”), which when activated by an electrical signal causes initiation of a detonator or explosive to detonate the corresponding shaped charge 110.

In accordance with one or more embodiments of the present disclosure, a shaped charge 110 has an outer casing that is formed of sintered metal powders. When exploded, the sintered metal powder casing would produce finer particles or debris, which would cause less damage to a perforating gun. Those skilled in the art would appreciate that other shaped charges may be used in accordance with one or more embodiments of the present disclosure.

FIG. 2 illustrates a schematic view of a conventional perforating gun 150, which includes a detonator 152 and a single detonating cord 154 with multiple shaped charges 156 arranged along a length of the detonating cord 154. Because the shaped charges 156 are stringed in series on the detonating cord 154 at different lengths from the detonator 152, they will fire at different times, which may result in charge interference. Therefore, the perforating gun 150 is designed with a sufficient spacing Y between the shaped charges 156 to reduce charge interference and allow greater penetration depth. However, the spacing required reduces the number of shaped charges that may be packed in a perforating gun, and thus, lowers the charge packing density of the perforating gun.

Referring now to FIG. 3, which shows a schematic view of groups of shaped charges of a perforating gun 200 in accordance with one or more embodiments of the invention. As shown, perforating gun 200 includes a detonator 202 and a plurality of detonating cords 204 attached to the detonator 202. The detonating cords 204 have a plurality of shaped charges 206 attached at various distances along lengths thereof. The plurality of shaped charges form groups of shaped charges at the various distances.

In this example, the shaped charges 206 are arranged along the detonating cords 204 to form three groups of charges at different lengths along the detonating cords 204. For example, at a first distance along the detonating cords 204 from the detonator 202, a plurality of shaped charges 206 form a first group of shaped charges, or Group A as shown in FIG. 3. Similarly, at a second distance along the detonating cords 204 from the detonator 202, s plurality of shaped charges 206 form a second group of charges, or Group B. As shown in FIG. 3, the second group of shaped charges Group B is spaced at certain distance X from the first group of charges Group A. Still further, at a third distance along the detonating cords 204 from the detonator 202, a plurality of shaped charges 206 form a third group of charges, or Group C. Likewise, the third group of shaped charges Group C is spaced a certain distance X′ from the second group of shaped charges Group B. In certain embodiments, distances X and X′ between the different groups of shaped charges may be the same or substantially equal. In other embodiments, distances X and X′ between the different groups of shaped charges may vary. The distances X and X′ may be designed to reduce interference between the neighboring groups of shaped charges. One skilled in the art would appreciate that the actual distances X and X′ required would depend on various factors (e.g., types and amounts of the explosives in the shaped charges, the materials used to construct various parts of shaped charges, etc.) and the proper distances can be determined without inventive efforts once the types of shaped charges are chosen.

In accordance with embodiments of the invention, shaped charges in the same group are designed to fire at the same time. One approach is to have the same length of detonating cords connecting between the detonator 202 the shaped charges 206 within the same group. To maintain equal distances from the detonator 202 for the same group of individual shaped charges 206 along multiple detonating cords 204, different distances at which different groups of shaped charges 206 are to be positioned may be marked along the multiple detonating cords 204. For example, a first distance from the detonator may be marked along all detonating cords 204 at which the first group of shaped charges 206 will be positioned. Likewise, a second distance from the detonator may be marked along the multiple detonating cords 204 at which the second group of shaped charges 206 will be positioned. Still further, any subsequent distances from the detonator may be marked along the multiple detonating cords 204 at which any subsequent groups of shaped charges 206 will be positioned.

Alternatively, the detonating cords 204 may be pre-marked with distance markers along lengths of the detonating cords 204. Then, one can simply count the marks to determine where to attach the shaped charges 206 during assembly. By having distance markers along lengths of the detonating cords 204, it would be easier to assemble a perforating gun of the invention and to avoid mistakes.

In this manner, regardless of whether the detonating cords 204 are pulled tight or have some slack in them when packed in the perforating gun, the distance along all detonating cords 204 from the detonator 202 to the first group of shaped charges (i.e., Group A) would be substantially equal, and thus, the first group of shaped charges will be ignited simultaneously. Likewise, the distance along all detonating cords 204 from the detonator 202 to the second group of shaped charges (i.e., Group B) would be substantially equal, and thus, the second group of shaped charges will be ignited simultaneously, and so on with additional groups of subsequent shaped charges.

In the above example, multiple detonating cords are connected to the detonator and the multiple shaped charges. In other embodiments of the invention, some segments of the detonating cords may be shared and one or more splitters may be used, as illustrated in FIG. 4.

Referring to FIG. 4, in still further embodiments, a perforating gun 300 may have splitters 304 (i.e., one input/multiple outputs) for detonating cords 304 to provide equal distances to the groups of shaped charges 306. As shown, an input branch 305 of a first splitter 304 extends from the detonator 302, and multiple output branches 307 of the first splitter 304 are attached to the shaped charges 306. Moreover, an input branch 315 of a second splitter 314 extends from a shaped charge 306 in the first group of charges, and multiple output branches 317 of the second splitter 314 are attached to shaped charges 306 in a second group of charges. Additional splitters (not shown) may be used for additional groups of charges in similar manner. Also, while the input branch of the second splitter 314 is shown as extending from a middle shaped charge 306, the input branch of the splitters may extend from any of the shaped charges in the previous group in accordance with one or more embodiments of the present disclosure. Furthermore, in a perforating gun, one may mix different types of detonating cord configurations—i.e., individual detonating cords for individual shaped charges as in FIG. 3 for some groups of shaped charges and splitter configuration as in FIG. 4 for other groups of shaped charges.

While only three groups of shaped charges 206 (i.e., Group A, Group B, and Group C) are shown in FIG. 3, those skilled in the art will appreciate that fewer groups (e.g., one or two) or more groups (e.g., four, five or more) of shaped charges 206 may be included in a perforating gun. Furthermore, while three detonating cords 204 are shown in FIG. 3, those skilled in the art will appreciate that any number of detonating cords 204 with shaped charges therealong may be used.

The shaped charges in a group are preferably evenly spaced about a circumference of the perforating gun in accordance with one or more embodiments of the present disclosure. For example, in certain embodiments three shaped charges 206 may be evenly spaced at 120 degree intervals about a circumference of the perforating gun. In other embodiments, two shaped charges 206 may be spaced 180 degrees apart about a circumference of the perforating gun. In still further embodiments, four shaped charges 206 may be spaced 90 degrees apart about a circumference of the perforating gun. In alternative embodiments, any number of shaped charges 206 may be unevenly spaced about a circumference of the perforating gun.

Some embodiments of the invention relate to methods of using a perforating gun having shaped charges in a group configured to ignite at the same time (or substantially the same time). The shaped charges in a group may be at an equal distance from the detonator along multiple detonating cords. Further groups of shaped charges may be included in the perforating gun, wherein all shaped charges in the same group are configured to ignite at the same time. Thus, the same length of detonating cord may be used from the detonator to each individual shaped charge in a first group (i.e., Group A). Likewise, the same length of detonating cord may be used from the detonator to each individual shaped charge in a second group (i.e., Group B), and so on for additional groups of charges. The spacing between the neighboring groups of shaped charges should be sufficient to prevent charge interference between adjacent groups of shaped charges. Simultaneous initiation of the first group of charges occurs when the ignition charge travels along the detonating cords from the detonator to the first group. Subsequently, simultaneous initiation of the second group of charges occurs when the ignition charge travels along the detonating cords from the first group of charges to the second group. Simultaneous initiation of any subsequent additional groups of charges occurs in the same manner until all groups of charges have been reached.

In accordance with methods of the invention, such perforating guns may be deployed in a wellbore. Then, the perforating gun is fired to ignite shaped charges in each group. Because shaped charges in a group ignite at the same time, they can achieve better penetration.

Some embodiments of the invention relate to methods for manufacturing perforating guns of the invention. In accordance with embodiments of the invention, multiple shaped charges would be disposed in a perforating gun housing to form a group. Then, detonating cords are used to connect these shaped charges to a detonator of the perforating gun. The detonating cords are configured to provide simultaneous ignition of the multiple shaped charges in the same groups. This may be achieve by having the same length of the detonating cords connecting the shaped charges to the detonator.

When the same lengths of detonating cords are used, one may mark the multiple detonating cords for the multiple shaped charges in the same group, and then connect the shaped charges to the marked locations on the multiple detonating cords. Alternatively, one may have detonating cords pre-marked with distance markers, and then count the distance markers to get the same distances during assembly.

Advantages of embodiments of the invention may include one or more of the following. Embodiments of the present disclosure provide a perforating gun with a higher packing density of shaped charges and reduced charge interference among shaped charges. The simultaneous initiation of multiple spaced groups of charges allows for more shaped charges to be disposed at a particular location for greater perforating energy, while avoiding the hindrances of charge interference.

Although only a few example embodiments have been described in detail above those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function. 

1. A perforating gun comprising: a plurality of shaped charges located at a first distance from a detonator along a plurality of detonating cords and forming a first group, wherein the plurality of shaped charges in the first group are configured to be detonated simultaneously.
 2. The perforating gun of claim 1, further comprising a plurality of shaped charges located at a second distance from the detonator along the plurality of detonating cords and forming a second group, wherein the plurality of shaped charges in the second group are configured to be detonated simultaneously.
 3. The perforating gun of claim 1, wherein the plurality of shaped charges are evenly spaced around a circumference of the perforating gun.
 4. The perforating gun of claim 1, wherein the plurality of shaped charges are unevenly spaced around a circumference of the perforating gun.
 5. The perforating gun of claim 1, wherein the plurality of detonating cords are of the same length.
 6. The perforating gun of claim 1, wherein the plurality of detonating cords are pre-marked with distance markers along their lengths.
 7. The perforating gun of claim 1, wherein the plurality of detonating cords comprises a splitter having a single input and multiple outputs.
 8. A method for manufacturing a perforating gun, the method comprising: positioning a plurality of shaped charges in a housing of the perforating gun, wherein the plurality of shaped charges are disposed at a first distance from a detonator; and connecting a plurality of detonating cords to each of the plurality of shaped charges, wherein the plurality of detonating cords are configured to provide simultaneous detonation of the plurality of shaped charges.
 9. The method of claim 8, wherein the plurality of detonating cords are of the same length.
 10. The method of claim 8, wherein the plurality of detonating cords are pre-marked with distance markers along their lengths.
 11. A method for using a perforating gun, the method comprising: providing the perforating gun in a borehole, wherein the perforating gun comprises: a plurality of shaped charges located at a first distance from a detonator along a plurality of detonating cords and forming a first group, wherein the first group of shaped charges is configured to be detonated simultaneously; and detonating the perforating gun to fire the plurality of shaped charges simultaneously.
 12. The method of claim 11, wherein the plurality of detonating cords are of the same length.
 13. The method of claim 8, wherein the plurality of detonating cords are pre-marked with distance markers along their lengths. 